I've just had some problems getting this working, which seem to be down to the way that alarmed calls python. From a default install under PR1.2, alarmed crashed after 7-8 seconds of the progress indicator spinning around, and returned me to the desktop. Based on previous debug instructions, I tried to run /opt/alarmed/alarmed.py, which produced the error
I checked that python was indeed installed; according to dpkg it was, but no binary called 'python' to be found on the system. After some head-scratching, it turns out to be because the python binary is installed as /usr/bin/python2.5 while alarmed is looking for a binary called just python.
and it worked. :-)

You may like to consider making alarmed die with a suitable error message if it can't find the python interpreter, or making alarmed look for python2.5, or creating the symlink during installation, if exists /usr/bin/python2.5 and not /usr/bin/python.

Regards,
Keith